Flexible heart valve

ABSTRACT

A highly flexible tissue-type heart valve is disclosed having a structural stent in a generally cylindrical configuration with cusps and commissures that are permitted to move radially. The stent commissures are constructed so that the cusps are pivotably or flexibly coupled together at the commissures to permit relative movement therebetween. The stent may be cloth-covered and may be a single element or may be made in three separate elements for a three cusp valve, each element having a cusp portion and two commissure portions; adjacent commissure portions for each pair of adjacent stent element combining to form the stent commissures. If the stent has separate elements their commissure portions may be pivotably or flexible coupled, or may be designed to completely separate into independent leaflets at bioresorbable couples. The cloth covering may have an outwardly projecting flap that mates with valve leaflets (e.g., pericardial leaflets) along the cusps and commissures. A connecting band may be provided that follows the cusps and commissures and extends outwardly. The valve is connected to the natural tissue along the undulating connecting band using conventional techniques, such as sutures. The connecting band may be a cloth-covered silicon member and attaches to the underside of the valve at the cusps to provide support to the stent and to the outer side of the valve at the commissures. A multi-legged holder is used to implant the valve, with the legs serving to maintain an implant shape to the valve. The holder may have six legs with one releasably connected to each cusp and one releasably connected to each commissure. A method of implantation of the flexible valve using the holder is also disclosed.

RELATED APPLICATION

The present application claims priority under 35 U.S.C §119(e) toprovisional application No. 60/117,445, filed on Jan. 26, 1999 under thesame title.

FIELD OF THE INVENTION

The present invention relates to prosthetic heart valves, and, moreparticularly, to a prosthetic tissue valve having increased flexibilityenabling it to follow the motions of the annulus and sinus regions.

BACKGROUND OF THE INVENTION

Prosthetic heart valves are used to replace damaged or diseased heartvalves. In vertebrate animals, the heart is a hollow muscular organhaving four pumping chambers: the left and right atria and the left andright ventricles, each provided with its own one-way outflow valve. Thenatural heart valves are identified as the aortic, mitral (or bicuspid),tricuspid and pulmonary valves. The valves of the heart separatechambers therein, and are each mounted in an annulus therebetween. Theannuluses comprise dense fibrous rings attached either directly orindirectly to the atrial and ventricular muscle fibers. Prosthetic heartvalves can be used to replace any of these naturally occurring valves,although repair or replacement of the aortic or mitral valves are mostcommon because they reside in the left side of the heart where pressuresare the greatest. In a valve replacement operation, the damaged leafletsare excised and the annulus sculpted to receive a replacement valve.

The four valves separate each ventricle from its associated atrium, orfrom the ascending aorta (left ventricle) or pulmonary artery (rightventricle). After the valve excision, the annulus generally comprises aledge extending into and defining the orifice between the respectivechambers. Prosthetic valves may attach on the upstream or downstreamsides of the annulus ledge, but outside of the ventricles to avoidinterfering with the large contractions therein. Thus, for example, inthe left ventricle a prosthetic valve is positioned on the inflow sideof the mitral valve annulus (in the left atrium), or on the outflow sideof the aortic valve annulus (in the ascending aorta).

Two primary types of heart valve replacements or prostheses are known.One is a mechanical-type heart valve that uses a ball and cagearrangement or a pivoting mechanical closure to provide unidirectionalblood flow. The other is a tissue-type or “bioprosthetic” valve which isconstructed with natural-tissue valve leaflets which function much likea natural human heart valve, imitating the natural action of theflexible heart valve leaflets which seal against each other to ensurethe one-way blood flow.

Prosthetic tissue valves comprise a stent having a rigid, annular ringportion and a plurality of upstanding commissures to which an intactxenograft valve or separate leaflets of, for example, bovine pericardiumare attached. The entire stent structure is typically cloth-covered anda sewing ring is provided around the periphery for attaching to thenatural annulus. Because of the rigidity of the material used in thestent and/or wireform, conventional valves have a diameter that isminimally affected by the natural motion of the heart orifice. In theaortic position, the commissures extend in the downstream direction aspaced distance from the walls of the downstream aortic wall. Movementof the aortic wall or sinuses does not directly affect movement of thecantilevered commissures, though fluid flow and pressures generated bymovement of the walls ultimately does cause the commissures todynamically flex to some extent (i.e., they are cantilevered downstreamin the aorta). Because of the inherent rigidity in conventional heartvalves, the natural dilatation of the annulus is restricted, imposing anartificial narrowing of the orifice, and increasing the pressure droptherethrough.

Accordingly, there is a need for a more flexible heart valve thatresponds to the natural motions of the annulus and downstream vesselwalls.

SUMMARY OF THE INVENTION

The present invention allows the prosthesis to follow the aortic wallmotion as well as that of the annulus during systole and diastolephases, thus reducing the loss in pressure caused by restriction of suchmotions. The solution is a heart valve having a plurality of leaflets,preferably three, directly sutured to the aortic wall, replacing thenative valve.

The present invention provides a heart valve including a flexiblewireform or stent that allows relative cusp movement or pivoting. Thecontinuous maintenance of leaflet orientation at the commissuresprovides durability and predictability. Though the leaflets are notwholly independent, they are allowed to move in regions of greatestanatomical motion.

The present invention differs in another respect from bioprosthetictissue valves of the prior art because it does not include aconventional sewing ring with attendant rigid stent. Alternatingperipheral cusps and commissures of the prosthetic valve are attached tothe annulus region and the sinus region of the ascending aorta of thehost (in the aortic valve version), downstream from the location of thenatural leaflets (typically excised).

In accordance with one aspect of the present invention, a prostheticheart valve is provided including a flexible, generally cylindricalstent having alternating cusps and commissures. A plurality of flexibleleaflets is attached to the stent so as to form a one-way valve withinthe cylinder. A flexible band is attached along the stent and has a freeedge extending away from the stent along the alternating cusps andcommissures for connecting the heart valve to an anatomical orifice.

Another aspect of the present invention is a highly flexible heart valveincluding a stent/leaflet subassembly having a peripheral stent and aplurality of leaflets disposed therewithin. The stent/leafletsubassembly defines alternating cusps and the commissures. A connectingband is attached to the stent/leaflet subassembly and follows thealternating cusps and commissures. The band includes a free edgeextending from the stent for connecting the heart valve to an anatomicalorifice.

In a still further aspect of present invention, a prosthetic heart valvecomprises a plurality of flexible leaflets, each having an arcuate cuspedge and a coapting edge. The heart valve includes a stent with aplurality of cusps connected to each other at upstanding commissures togenerally define a substantially cylindrical volume therebetween. Theleaflets are attached to the stent within the cylindrical volume and thecusps are free to move with respect to one another about thecommissures.

In another embodiment, the present invention provides a prosthetic heartvalve comprising a stent having a plurality of stent members adjacentlydisposed generally around a circle to define a substantially cylindricalvolume therebetween. The stent includes a plurality of alternating cuspsand commissures. Preferably, the stent members each have a cusp and twocommissure regions, with adjacent commissure regions of the stentmembers together defining each of the commissures of the stent. Thestent members may be coupled together to pivot or flexibly move withrespect to one another. The coupling may be permanent, or may comprise abio-resorbable structure that permits the stent members and associatedleaflets to move independently from one another.

Desirably, the stent of the prosthetic heart valve of the presentinvention is configured to permit the cusps and commissures to moveradially in and out. In one embodiment, the stent comprises a clothcovered rod-like structure. The cloth covering closely surrounds thestent and includes a flap projecting therefrom substantially the entirelength of the cusps and commissures for connecting the stent to both theflexible band and the leaflets. The band preferably comprises asuture-permeable inner member, such as silicone, covered by cloth. Thecusps of the stent may be pivotally or flexibly coupled to each other atthe commissures. Preferably, the stent comprises separate cloth-coveredstent members that each define a cusp region and two commissure regions,adjacent commissure regions of the stent members together defining eachof the commissures of the stent. The commissure regions of the separatestent members desirably remain spaced apart, with the leaflets extendingtherethrough to be attached between the cloth covering and the outerconnecting band. In this manner, the leaflets are connected to separatestent members, and not to each other to facilitate flexing of the valve.

In another aspect of the present invention, a holder is provided formounting the flexible heart valve. The holder includes a central hubwith a plurality of radially outward upper legs, and a plurality oflower legs angled downward and outward. The upper and lower legs areadapted to connect to the alternating cusps and commissures of aflexible valve so as to maintain the position of the valve duringimplantation.

The present invention further provides a combination of a flexibleprosthetic heart valve and a rigid holder. The flexible heart valveincludes alternating cusps and commissures in a generally cylindricalconfiguration adapted to move radially in and out with respect to oneanother. The holder includes structure for maintaining a fixed shape ofthe flexible prosthetic heart valve during implantation.

In a still further aspect of the present invention, a heart valveleaflet is provided comprising a flexible, planar body having an arcuatecusp edge terminating at outer tips. The planar body includes a coaptingedge that is defined by two relatively angled lines joined at an apexdirected away from the cusp edge midway between the two tips. Desirably,the leaflet is made of pericardial tissue.

The present invention further provides a method of implantation of aheart valve, including the steps of: providing a flexible heart valvehaving alternating cusps and commissures in a generally cylindricalconfiguration and adapted to move radially in out with respect to oneanother; attaching a holder to the valve that restricts relativemovement of the cusps and commissures; positioning the heart valve inproximity to an anatomical orifice; implanting the heart valve; and,disconnecting the holder from heart valve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view through the left half of a human heartshowing a systolic phase of left ventricular contraction;

FIG. 2 is a sectional view through the left half of a human heartshowing a diastolic phase of left ventricular expansion;

FIG. 3 is an exploded perspective view illustrating sub-assemblies of aprosthetic heart valve of the present invention;

FIG. 4A is a top plan view of an internal stent of the prosthetic heartvalve of the present invention;

FIG. 4B is an elevational view of the internal stent of FIG. 4A;

FIG. 5 is an elevational view of a stent assembly of the prostheticheart valve;

FIGS. 6A and 6B are sectional views through two locations of the stentassembly, taken along lines 6A—6A and 6B—6B of FIG. 5;

FIGS. 7A, 7B, and 7C are plan views of leaflets suitable for use in theprosthetic heart valve of the present invention;

FIG. 8 is an exploded perspective view of a stent/leaflet sub-assemblyand a connecting band of the prosthetic heart valve of the presentinvention;

FIG. 9 is an elevational view of an inner member of the connecting band;

FIG. 10 is a cross-sectional view through a cusp of the connecting bandshown in FIG. 8;

FIG. 11 is a perspective view of an assembled prosthetic heart valve ofthe present invention;

FIG. 12A is a cross-sectional view through a cusp region of theprosthetic heart valve of the present invention, taken along line12A—12A of FIG. 11, and showing a portion of the host annulus inphantom;

FIG. 12B is a cross-sectional view through a commissure region of theprosthetic heart valve of the present invention, taken along line12B—12B of FIG. 11, and showing a portion of the host aortic wall inphantom;

FIG. 13 is a schematic view showing relative movement of the aortic andannulus walls during systolic flow;

FIG. 14A is a plan view of only the stent members of the prostheticvalve flexed in accordance with the anatomical motions during systoleshown in FIG. 13;

FIG. 14B is an elevational view of the stent members flexed inaccordance with the anatomical motions during systole shown in FIG. 13;

FIG. 15 is a schematic view showing relative movement of the aortic andannulus walls during diastolic flow;

FIG. 16A is a plan view of only the stent members of the prostheticvalve flexed in accordance with the anatomical motions during diastoleshown in FIG. 15;

FIG. 16B is an elevational view of the stent members flexed inaccordance with the anatomical motions during diastole shown in FIG. 15;

FIG. 17 is a perspective view of an alternative stent assembly for usein a prosthetic heart valve in accordance with the present invention;

FIG. 18 is a perspective view of an internal stent of the stent assemblyof FIG. 17;

FIG. 19 is an exploded view of a commissure tip region of the stentassembly of FIG. 17;

FIGS. 20A-20E are elevational views of alternative stents for use in aprosthetic heart valve in accordance with the present invention;

FIG. 21 is a detailed view of a commissure region of the alternativestent of FIG. 20E;

FIG. 22 is a detailed view of a commissure region of a still furtheralternative stent accordance with the present invention;

FIG. 23 is an exploded perspective view of the prosthetic heart valve ofthe present invention and a holder used during implantation of thevalve;

FIG. 24 is a perspective view of the holder coupled to the valve;

FIG. 25 is a top plan view of the holder coupled to the valve;

FIG. 26 is a cross-sectional view through the holder and valve, takenalong line 26—26 of FIG. 25; and

FIGS. 27A and 27B are perspective views of an alternative holder for theprosthetic heart valve of the present invention used during implantationof the valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a highly flexible aortic heart valve thatis attached generally along a scalloped or undulating perimeterdownstream from where the natural leaflets were originally attached. Thenatural leaflets include arcuate cusp portions separated by commoncommissure portions. If the natural valve has three leaflets, and has avertically oriented flow axis, the leaflets are evenly distributedcircumferentially 120° apart with lower cusp portions and upstandingcommissure portions. The commissure portions are connected between thecusp portions and are generally axially aligned along the aortic wall.The annular root of an aortic valve is composed of fibrous tissue andgenerally conforms to the undulating perimeter of the valve to supportthe leaflets. In this respect, implanting the aortic heart valve of thepresent invention involves excising the natural leaflets and attachingthe prosthetic heart valve proximate the fibrous annulus, but also inpart up the aortic wall. Because of the particular construction of thepresent heart valve, as will be described below, the attachment means,be it sutures, staples, adhesives, or otherwise, may be anchored intothe aortic wall itself, adjacent to the fibrous annulus.

Anatomy

To better illustrate the advantages of the flexible heart valve of thepresent invention, an understanding of the movement of the annulus andaorta is helpful. In this regard, FIGS. 1 and 2 illustrate the twophases of left ventricular function; systole and diastole. Systolerefers to the pumping phase of the left ventricle, while diastole refersto the resting or filling phase. FIGS. 1 and 2 illustrate in crosssection the left chamber of the heart with the left ventricle 20 at thebottom, and the ascending aorta 22 and left atrium 24 diverging upwardfrom the ventricle to the left and right, respectively. FIG. 1illustrates systole with the left ventricle 20 contracting, while FIG. 2illustrates diastole with the left ventricle dilating. The aortic valve28 is schematically illustrated here as having leaflets 30. Contractionof the ventricle 20 causes the mitral valve 26 to close and the aorticvalve 28 to open, and ejects blood through the ascending aorta 22 to thebody's circulatory system, as indicated in FIG. 1 by the arrows 32.Dilation of the ventricle 20 causes the aortic valves 28 to close andmitral valve 26 to open, and draws blood into the ventricle from theleft atrium 24, as indicated in FIG. 2 by the arrows 33.

The walls of the left chamber of the heart around the aortic valve canbe generally termed the annulus region 34 and the sinus region 36. Theannulus region 34 generally defines an orifice that is the narrowestportion between the ventricle 20 and ascending aorta 22, which as notedabove is composed of generally fibrous tissue. The sinus region 36 isthat area just downstream from the annulus region 34 and includessomewhat elastic, less fibrous tissue. Specifically, the sinus region 36typically includes three identifiable, generally concave sinuses(formally known as Sinuses of Valsalva) in the aortic wall intermediatethe upstanding commissures of the valve 28. The sinuses are relativelyelastic and are constrained by the intermediate, more fibrouscommissures of the aortic annulus. Those of skill in the art willunderstand that the annulus region 34 and sinus region 36 are notdiscretely separated into either fibrous or elastic tissue, as thefibrous commissures of the annulus extend into the sinus region 36.

The sinuses tend to move in and out to facilitate fluid dynamics of theblood in conjunction with systole and diastole. During systole, as seenin FIG. 1, the sinus region 36 expands somewhat to a diameter A. Thisfacilitates blood flow through the ascending aorta 22 to the rest of thebody. In contrast, during the diastolic phase as seen in FIG. 2, thesinus region 36 contracts somewhat to a smaller diameter B. Thediameters A and B are intended to be a measurement of the radialmovement of the commissure regions of the valve 28. In this regard itwill be understood that the cross-sections shown are not taken in asingle plane, but instead are taken along two planes angled apart 120°with respect one another and meeting at the midpoint of the aorta 22.The sinus region 36 has a neutral, or relaxed diameter (not shown)somewhere in between diameters A and B.

The annular region 34 also moves in and out during the systolic anddiastolic phases. As seen in FIG. 1, the annular region 34 contractssomewhat to a diameter C during systole. In contrast, during thediastolic phase as seen in FIG. 2, the annular region 34 expandssomewhat to a larger diameter D. Much like the sinus region 36, theannular region 34 has a neutral, or relaxed diameter (not shown)somewhere in between diameters C and D.

As will be explained more fully below, the prosthetic valve of thepresent invention accommodates the in and out movements of both theannular region 34 and the sinus region 36. That is, alternatingperipheral portions of the prosthetic valve are attached to the annularregion 34 and the sinus region 36 and move accordingly. It is importantto point out that the preceding discussion of dynamic movement of theannulus and sinus regions is based on preliminary understanding of suchmovement. That is, direct measurements of these movements areproblematic, and thus certain assumptions and predictions must be made.The actual dynamic movement in any particular human heart may bedifferent, but the principles of the present invention would stillapply. That is, relative movement in the annulus and sinus regionsduring systole and diastole does exist, and the flexible prostheticheart valve of the present invention can accommodate any such movement.

Valve Subassemblies

With reference now to FIG. 3, the primary sub-assemblies of a preferredembodiment of the prosthetic heart valve 40 of the present invention areshown in exploded view. For purposes of discussion, the directions upand down, upper and lower, or top and bottom, are used with reference toFIG. 3, but of course the valve can be oriented in any direction bothprior to and after implantation. From top to bottom, the heart valve 40comprises a group 41 of three leaflets 42, three angled alignmentbrackets 44, a stent assembly 46, and a connecting band 48. Each of thesub-assemblies seen in FIG. 3 is procured and assembled separately(except for the group of leaflets, as will be explained), and thenjoined with the other sub-assemblies to form the fully assembled valve40 as seen in FIG. 11.

The prosthetic valve 40 is a trifoliate valve with three leaflets 42.Although three leaflets are preferred, and mimic the natural aorticvalve, the principles of the present invention can be applied to theconstruction of a prosthetic valve with two or more leaflets, dependingon the need.

Each of the sub-assemblies seen in FIG. 3 include three cusps separatedby three commissures. The leaflets 42 each include an arcuate lower cuspedge 50 terminating in upstanding commissure regions 52. Each leaflet 42includes a coapting or free edge 54 opposite the cusp edge 50. In theassembled valve 40, the cusp edges 50 and commissure regions 52 aresecured around the periphery of the valve, with the free edges 54permitted to meet or “coapt” in the middle. The stent assembly 46 alsoincludes three cusps 60 separated by three upstanding commissures 62. Inlike manner, the connecting band 48 includes three cusp portions 64separated by three upstanding commissure portions 66. Each of thesub-assemblies will now be described in detail.

Stent Assembly

Various components of a preferred stent assembly 46 are seen in FIGS.4-6. The stent assembly 46 comprises an inner stent 70 and an outercloth cover 72. More specifically, the inner stent 70 desirably includesthree identical and separate stent members 74, each of which has aseparate cloth covering. As seen best in FIG. 4B, each stent member 74comprises an arcuate lower cusp region 76 and upstanding commissureregions 78 each terminating at a tip 80. The stent members 74 compriseelongate rods or wires, preferably made out of an elastic biocompatiblemetal and/or plastic alloy, such as Elgiloy®, Nitinol, polypropylene,etc. The material selected for stent members 74 should be elastic topermit flexing along their lengths, but should possess a relatively highmodulus of elasticity to avoid asymmetric deformation of the constructedvalve 40. The stent 70 supplies an inner frame for the valve 40 that isrelatively more rigid than the other components. Therefore, the stent 70acts to limit total flexibility of the valve 40.

The stent members 74 are desirably bent into the illustrated shape,using conventional wire-forming techniques. Each of the stent members 74is identical, and terminates in the tips 80 which are bent inward withrespect to the arcuate cusp regions 76 to nearly form closed circles. Asis seen in FIG. 4B, a gradual radially outward bend 82 (with respect tothe cylindrical stent 70) is provided in the stent members 74 at atransition between each of the commissure regions 78 and theintermediate cusp region 76. This bend 82 permits each of the stentmembers 74 to remain in a circular configuration, as seen from above inFIG. 4A. That is, if the cusp regions 76 extended in a plane betweeneach of the commissure regions 78, the plan view would be somewhattriangular. Instead, each of the cusp regions 76 includes a lower apex84, and the apices of all of the cusps define a circle concentric withand having the same diameter as a circle defined by all of the tips 80.The stent 70 thus defines a substantially cylindrical volumetherewithin. Of course, other volumes may be defined by the stent 70wherein the tips 80 define a circle that is smaller or larger than acircle defined by the apices 84. For example, the apices 84 may beprovided outward from the tips 80 so the stent 70 defines afrusto-conical volume therewithin.

As seen in FIG. 5, each of the stent members 74 is preferably coveredwith a generally tubular cloth 72 from tip to tip 80. The cloth cover 72is a biocompatible fabric, such as polyterephthalate, and has a varyingcross sectional shape, as indicated in FIGS. 6A and 6B. Morespecifically, the cloth cover 72 includes a tubular portion closelyconforming around each of the stent members 74 and a flap 86 extendingradially outward from the stent member (with respect to the curvature ofthe cusp regions 76). The cloth cover 72 is formed by wrapping anelongated sheet of fabric around each of the stent members 74 andjoining the free edges with sutures 88 to form the flaps 86. As seen inFIG. 5, the flap 86 extends from each stent member 74 in a directionthat is generally outward with respect to the cusp region 76, andcontinues in the same general orientation up the commissure regions 78to the tips 80. The flap 86 has a dimension that is longest at the apex84 of each cusp region 76 and shortest at the tips 80. Indeed, the flap86 is preferably nonexistent at the tips 80, and gradually increases insize from the tip 80 to the apex 84. Therefore, the cross-section ofFIG. 6A taken through the commissure region 78 shows the flap 86 havinga small dimension d1, and the cross-section of FIG. 6B taken through theapex 84 shows the flap 86 having a longer dimension d2.

The final component of the stent assembly 46 is an attachment means 90for joining each of a cloth-covered stent members 74. Preferably, theattachment means 90 comprises threads or sutures sewn through thecentral holes in each of the circular tips 80, as shown in FIG. 5,although other suitable attachment means could be used, such as rings,cinches, or the like. The attachment means 90 may be wrapped around orsewn through the cloth cover 72. In joining the tips 80, the attachmentmeans 90 are desirably not wrapped extremely tightly, but are insteadprovided with some slack to permit relative movement of the tips, aswill be described below. When the stent members 74 are attached, as seenin FIG. 5, the stent 70 exhibits three cusps corresponding to the cuspregion 76 of each member, and three upstanding commissures defined bythe juxtaposition of adjacent pairs of commissure regions 78.

In a preferred embodiment of the present invention the attachment means90 comprises a non-bioresorbable material to ensure that the individualstent members 74 are maintained in the shape of the stent 70. In analternative configuration, however, the attachment means 90 comprises abioresorbable material that dissolves over a period of time afterimplantation. In such an embodiment, the natural host tissues may havegrown in and around the porous portions of the valve 40 to help retainthe original shape of the stent 70. In some instance, however, verylittle tissue overgrowth may have occurred prior to the attachment means90 dissolving, and the individual stent members 74 are permitted to moveradially a great deal with respect to one another. In the latterembodiment, wherein the stent members 74 are permitted to spread apart,the connecting band 48 may be re-configured to be non-continuous at thecommissure portions 66 (see FIG. 3). As a consequence, each individualstent member 74 and associated leaflet 72 moves entirely independentlyof the others, albeit all oscillating with the natural contractions andexpansions of the surrounding aortic wall. Such independent leafletmovement may greatly reduce any potential pressure drop across thevalve. Although one embodiment is to provide a bioresorbable attachmentmeans 90 such as the sutures shown in the embodiment of FIG. 5, those ofskill in the art will understand that any of the coupling meansconnecting the individual stent members 74 disclosed in the presentapplication could be modified to resorb over time.

The stent assembly 46 provides an inner support frame that is generallyrigid along any one of stent members 74, but which permits the stentmembers to move with respect to one another. In this context, “generallyrigid” refers to the structural strength of the stent members 74 that issufficient to maintain the general shape of the stent 70, but thatpermits some flexing along the length of the stent members. Though thestent members 74 are generally rigid, they are able to move with respectto one another. More particularly, joining the stent members 74 with theattachment means 90 creates nodes or pivot points of the valve 40 at thecommissures 62 of the stent assembly 46. As will be more fully explainedbelow with reference to FIGS. 13-16, the stent members 74 are permittedto pivot with respect to one another as they move radially inward andoutward. Inward pivoting is permitted by spaces 94, seen in FIG. 5,defined between adjacent cloth-covered commissure regions 78 of eachstent member 74. These regions 94 are generally triangular and graduallyincrease in size from the attached commissure tips to the divergingcusps.

Leaflet Configurations

FIGS. 7A, 7B, and 7C are plan views of various configurations ofleaflets 42 suitable for use in the prosthetic heart valve 40. FIG. 7Ashows a leaflet 42 having the aforementioned cusp 50, commissure regions52, and free edge 54. It will be noted that the coapting edge 54comprises two linear portions extending from an apex 100 to outer tips102. The two portions of the free edge 54 are angled with respect to oneanother and define sides of a triangular region 104 having as itshypotenuse an imaginary line 106 extending between the opposed tips 102.The triangular region 104 of each leaflet 42 is under less tensionduring dynamic motion of the valve 40, and helps ensure coaptation ofthe leaflets. That is, the leaflets 42 are generally secured along thecusp 50 and commissure regions 52, and thus the majority of each leaflet42 is placed in stress except in the region above imaginary line 106. Inthis regard, an imaginary (dashed) fold line 108 defines an outer margin110 of the leaflet 42 that is used to secure the leaflets into the valve40. As will be clear from the discussion below, the margins 110 aresutured between the stent assembly 46 and connecting band 48 (FIG. 3),and the free edge 54 of the leaflet extends across the cylindricalregion defined within the valve 40, and is generally free to move inthat region. Because the triangular leaflet region 104 is relativelystress-free, it tends to roll over under the influence of fluid dynamicforces, thus helping the three leaflets to coapt and prevent valveinsufficiency.

FIG. 7B shows a leaflet 112 that is substantially the same as theleaflet 42 of FIG. 7A, and thus like elements will be given the samenumbers. The leaflet 112 includes a pair of generally triangular shapedcommissure tabs 114 in the commissure regions 52. The tips 102 are thusspaced farther apart than in the version shown in FIG. 7A. Thecommissure tabs 114 are used to more securely fasten each of theleaflets to the commissures 62 of the stent assembly 46 (FIG. 3). Thecloth cover 72 of the stent assembly 46 includes a flap 86 (FIG. 5)which diminishes in size in the commissure regions. The tabs 114 arethus wrapped farther around the cloth-covered stent assembly 46 in thecommissure regions and sutured thereto, thus facilitating a more durableconnection.

FIG. 7C is a further variation of a leaflet 116 which is, again, thesame in all respects to the leaflets described above, except forsomewhat trapezoidal-shaped commissure tabs 118. Again, the commissuretabs 118 help to secure the leaflets 116 in the prosthetic valve 40.

Stent/Leaflet Sub-assembly

FIG. 8 illustrates a stent/leaflet sub-assembly 120 in which theleaflets 42 are secured to the stent assembly 46. Preferably, leaflets42 are pre-attached to align the free edges 54. In this manner, the freeedges 54 of each two adjacent leaflets 42 extend outward injuxtaposition and are received within the triangular space 94 definedbetween the commissure regions 78 of the stent assembly 46 (FIG. 5). Thegroup of leaflets 41 is thus “inserted” underneath the stent assembly 46until the juxtaposed free edges 54 of the leaflets 42 are in closeproximity below the attachment means 90. The outer margin 110 of eachleaflet 42 is folded underneath the corresponding cusp 60 of the stentassembly 46. At this point, sutures or other such means attach themargins 110 to the flap 86 of the stent assembly 46. The leaflets 42 canremain attached to one another at their adjacent tips 102 (or along thefree edges 54 near the tips), or can be separated for maximum valveflexibility or when the stent is designed to separate into individualstent members by bio-resorption of a commissure couple.

If either the leaflet 112 or leaflet 116 of FIG. 7B or 7C are used, therespective commissure tabs 114 or 118 are wrapped around the adjacentpart of the stent assembly 46 and secured thereto. In a preferredassembly method, the leaflets 42 are simply retained in position withrespect to the stent assembly 46 with temporary sutures or other suchmeans, to permit the stent/leaflet subassembly 120 to be finally joinedtogether with the connecting band 48 of FIG. 8.

FIG. 8 also illustrates the three alignment brackets 44 and that eachhas a generally L-shaped cross-section and comprises a cloth-coveredinner member (not separately numbered). The inner member preferably hasminimum elasticity, but is relatively thin and lightweight. Onepreferred material for the inner member is a polyester film such asMylar®. The brackets 44 are preferably joined to the valve 40 at thetime the stent/leaflet sub-assembly 120 and connecting band 48 arejoined, and thus will be described more fully below with respect to FIG.11.

Connecting Band

FIGS. 9 and 10 illustrate the connecting band 48 in more detail,comprising an inner member 130 surrounded by a cloth cover 132. Asmentioned previously with respect to FIG. 3, the connecting band 48includes three cusp portions 64 alternating with commissure portions 66,all generally formed in a tubular configuration. This shape is providedby the inner member 130, with the cloth cover 132 simply draped and sewnthereover. In a preferred embodiment, the inner member 130 is molded ofsilicone rubber, and the cloth cover 132 is polyterephthalate.

The inner member 130 has a varying cross sectional shape along the cuspsand commissures. FIG. 10 is cross-section through one of the cuspportions 64 of the connecting band 48, and shows a region of the innermember 130 having an inner ledge 134 and upwardly angled outer freemargin 136. The cloth-covered ledges 134 extend generally radially anddefine three stent support regions 138 of the connecting band 48, asseen in FIG. 8. The ledge 134 has its greatest radial dimension at themidpoint of each of the cusp portions 64 and gradually tapers down insize toward the commissure portions 66. Likewise, the free margins 136form their greatest outward angle with respect to a central axis of theconnecting band 48 at each cusp portion 64, and gradually re-align to beparallel to the central axis in the commissure portions 66. Thecross-section of the inner member 130 at the commissure portions 66 isseen in FIG. 12B. A series of triangular shaped ribs 140 projectsoutward from the inner member 130. The ribs 140 are formed around theentire inner member 130, along both the cusp and commissure regions. Asseen in FIG. 8, the commissure portions 66 of the connecting band 48define generally axial gaps 142 that help permit flexing of the valve40. It should be noted that the connecting band 48 may be discontinuousat the commissure portions 66 if the valve has bioresorbable commissuresand is designed to separate into individual “leaflets.”

Assembled Valve

FIG. 11 illustrates the assembled valve 40 in perspective, while FIGS.12A and 12B show cross-sections through a valve cusp 150 and valvecommissure 152, respectively. The connecting band 48 is sewn orotherwise attached to the exterior of the stent/leaflet subassembly 120.Actually, as seen in FIG. 12A, the connecting band 48 is attachedunderneath the stent/leaflet subassembly 120 in the cusp 150, but thefree margins 136 of the connecting band are positioned to the outside ofthe subassembly. In addition, the alignment brackets 44 are installedwith a vertical leg 156 interposed between the commissures 62 of thestent assembly 46 and the commissure portions 66 (FIG. 3) of theconnecting band 48. A horizontal leg 154 of each of the alignmentbrackets 44 projects radially inward to cover the tips 80 of the stentassembly 46. The alignment brackets 44 help hold each two adjacent tips80 of the three-piece stent 70 together, especially helping to preventradial mis-alignment. The brackets also provide flat surfaces which aholder can contact, as seen best in FIG. 26.

With reference to the cross-section of FIG. 12A, the sandwichedconfiguration of the stent assembly 46, leaflet 42, and connecting band48 can be seen. More specifically, the cloth flap 86 of the stentassembly 46 aligns with the leaflet margins 110, which in turn rest onthe stent supports 138. A series of suture stitches 158 are used tosecure these elements together. Preferably, the flap 86 terminates atthe same location as the margin 110 of each leaflet 42, and at thecorner defined in the connecting band 48 between each ledge 134 and freemargin 136. The radially innermost wall of the ledge 134 is preferablyinward from the stent member 74. This construction helps prevent thestent 70 from migrating downward with respect to the connecting band 48.

The host annulus 162 is seen in phantom with the aortic wall 164continuing upward therefrom. It can be readily seen that the angledshape of the cusp portions 64 of the connecting band 48 conform nicelyto the host annulus region. The triangular ribs 140 provide volume atthe free margins 136 of the connecting band 48 to facilitate connectionto the natural tissue; in other words, more volume provides more of a“bite” for the surgeon to secure the band 48 with a suture needle.Although the conventional means for attaching the valve 40 to the hosttissue is with sutures, which are not shown, the present inventionshould not be construed as limited to being implanted with sutures andother means such as staples, adhesives, and the like could be used.

Now with reference to FIG. 12B, the assembly of the valve components inthe commissure region is seen. The commissure edges 52 of each of theleaflets 42 are sandwiched in between the stent assembly 46 andconnecting band 48. More particularly, the commissure edges 52 aresandwiched between the flaps 86 and the generally planar commissureportions 66 of the connecting band 48 (FIG. 8). Sutures 170 are providedto join these elements together. Again, the commissure edges 52preferably terminate at the same location as the flaps 86. FIG. 12B alsoillustrates the gap 142 provided in the commissure regions of theconnecting band 48, and the lack of structural connection between thetwo sides of each valve commissure 152.

FIG. 12B shows in phantom a portion of the aortic wall 172 to which thecommissures 152 (seen in FIG. 11) of the valve 40 are attached. Again,the particular attachment means is not shown, but the connecting band 48is traditionally sutured to the wall 172.

Dynamic Motion of the Prosthetic Heart Valve

FIGS. 13 and 15 illustrate a conduit portion of a heart in the region ofthe aortic valve and relative motions of the conduit walls duringsystole and diastole, respectively. In particular, FIG. 13 shows an openvalve 200 and systolic blood flow 202, while FIG. 15 shows a closedvalve 204 and diastolic back flow of blood 206. As described withrespect to FIGS. 1 and 2, the regions around the aortic valve can begenerally separated into an annulus region 208 and a sinus region 210.

As mentioned previously, the annulus region 208 is expected to contractduring the systolic phase, as indicated by the arrows 212 in FIG. 13,and expand during the diastolic phase, as indicated by the arrows 214 inFIG. 15. Conversely, the sinus region 210 is expected to expand duringthe systolic phase, as indicated by the arrows 216 in FIG. 13, and isexpected to contract during the diastolic phase, as indicated by thearrows 218 in FIG. 15. The movements of the conduit walls are shown withrespect to a neutral or relaxed position 220, and may be exaggeratedfrom the true movements. Also, as mentioned above, these movements areeducated guesses and may be different for some, if not most patients.However, the flexible heart valve of the present invention accommodatesall variations of such movements.

FIGS. 14 and 16 schematically illustrate the synchronous movement of theprosthetic valve 40 of the present invention with respect to themovements of the host tissue in systolic and diastolic phases as seen inFIGS. 13 and 15. To simplify this explanation, FIGS. 14 and 16 onlyillustrate the stent 70 of the present invention, which as previouslydescribed acts as a limitation to movement of the entire valve 40 andfairly represents movement of the entire valve.

With reference to FIGS. 14A and 14B, during systole the valveexperiences outward commissure movement, as indicated by the arrows 230.At the same time, the valve experiences inward movement at the cusps, asindicated by the arrows 232. During diastole, in contrast, and as seenin FIGS. 16A and 16B, the valve experiences inward commissure movement,as indicated by the arrows 234. At the same time, the valve experiencesoutward movement at the cusps, as indicated by the arrows 236.

Alternative Stents

FIGS. 17-19 illustrate an alternative stent assembly 250 comprising aninner stent 252 and an outer cloth cover 254. As with the earlier stentassembly 46, the stent assembly 250 includes alternating cusps 256 andcommissures 258. As best seen in FIG. 18, the stent 252 includes threeseparate stent members 260 having arcuate commissure tips 262 that arecurved toward one another. A generally disk-shaped commissure housing264 encompasses the adjacent commissure tips 262, retaining the stentmembers 260 together while permitting relative pivoting.

FIG. 19 illustrates two adjacent commissure tips 262 and the commissurehousing 264 exploded into a male housing portion 266 and a femalehousing portion 268. The housing portions are so named because they arejoined together through interference between a button 270 of the malehousing portion 266 and an aperture 272 on the female housing portion268. Each portion of the commissure housing 264 includes a circulargroove 274 for receiving the arcuate tips 262. The grooves 274 combinedto form a circular channel having an axis 276 within which the arcuatetips 262 are received and can slide. When assembled together, thecommissure housings 264 thus provide nodes of rotation for each of thestent members 260.

FIG. 20A illustrates an alternative stent 280 suitable for use in aheart valve of the present invention. The stent 280 includes three stentmembers 282, each having commissures with a flex region 284 and tips286. The tips 286 of adjacent stent members 282 are secured together bysutures or other suitable means (not shown). The flex regions 284comprise sections of each stent member 282 which are bent away from eachother. The stent members 282 can thus pivot with respect to one anotherabout the connected tips 286. Upon inward movement of the stent members282, a fulcrum 288 is created by interaction between the stent membersat the lower end of the flex region 284. The relative flexibility ininward or outward movement of the stent members 282 can be modified byselection of the cross sectional size and shape of the stent members,and overall configuration of the flex region 284.

FIG. 20B illustrates a second alternative stent 290 suitable for use ina heart valve of the present invention. The stent 290 includes threewires 292 and has commissure regions 294 formed by bent ends of thewires and a junction member 296. In this embodiment, the junction member296 either rigidly holds the terminal ends of each of the wires 292, orpermits the wires to slide or otherwise flex with respect to oneanother. If the wires are rigidly attached to the junction member 296the shape of the wires in the commissure region 294 reduces stressrisers in bending.

FIG. 20C illustrates a third alternative stent 300 suitable for use in aheart valve of the present invention. The stent 300 comprising threeseparate wires 302 terminating at circular commissure tips 304. Each ofthe commissure tips 304 is rotatably fastened around a pin 306 providedon a junction plate 308 common to adjacent wires 302. In this manner,the tips 304 remained located close to one another, while the cusps ofthe wires 302 can pivot in and out.

FIG. 20D illustrates a fourth alternative stent 310 suitable for use ina heart valve of the present invention. The stent 310 is made in onepiece with a series of alternating cusps 312 and commissures 314. Thecommissures 314 comprising a nearly 360° bend in the stent 310 whichpermits each cusp 312 to easily flex with respect to the other cusps.

FIG. 20E illustrates a fifth alternative stent 320 suitable for use in aheart valve of the present invention. The stent 320 comprises threewire-like stent members 322, adjacent ones of which are joined togetherat commissure regions 324 by a U-shaped coupling 326 and a pair flexiblesleeves 328. FIG. 21 is a detail of one of the commissure regions 324showing in hidden lines the adjacent ends of the coupling 326 and stentmembers 322. The couplings 326 are preferably sized with the samediameter as the stent members 322, and the sleeves 328 are tubular witha constant diameter lumen. The sleeves 328 may be made of silicone, or aflexible polymer such as polyurethane or the like. Other flexibleinterfaces such as sleeves 328 are contemplated, such as, for example, asingle block of silicone into which the commissure regions 324 of thestent members 322 are molded.

FIG. 22 is a detailed view of a commissure region 330 of a still furtheralternative stent suitable for use in a heart valve of the presentinvention. The stent is made in one piece with adjacent cusps 332 beingjoined by a coil spring tip 334. Again, great flexibility is provided bythe coil spring tips 334 to enable relative motion of the cusps 332. Theamount of flexibility is selected as in any spring by varying thematerial, cross-sectional size and shape, and number of turns of thespring.

Valve Holder

FIGS. 23-26 illustrate a preferred holder 350 useful for implanting theflexible heart valve 40 of the present invention. As the heart valve 40is relatively flexible, the holder 350 must provide adequate support toinsure a stable platform for the surgeon to position the valve forattachment to the natural tissue. In other words, because the flexibleprosthetic heart valve 40 of the present invention exhibits alternatingcusps and commissures in a generally cylindrical configuration that areadapted to move radially in and out with respect to one another, theholder 350 desirably provides rigid structure for maintaining a fixedshape of the valve during implantation. In addition, the holder 350 mustinclude structure to allow quick release from the valve 48 after thevalve is implanted.

As seen in FIG. 23, the holder 350 comprises a proximal handle socket352 having an inner bore 354 for receiving the distal end of a handle(not shown). The socket 352 may be provided with internal threads, orother such quick-release coupling structure to facilitate handleconnection and disconnection. The holder 350 has three radiallyoutwardly-directed commissure legs 356, and three outwardly anddownwardly angled cusp legs 358. Consistent with the distribution of thecusps 150 and commissures 152 of the valve 40, the commissure legs 356are oriented 120° apart, and the cusp legs 358 are oriented 120° apart,with the three commissure legs being offset with respect to the threecusp legs by 60°.

As seen in FIG. 24, each of the commissure legs 356 extends outward fromthe handle socket 352 into proximity with one of the valve commissures152 and is secured thereto with an upper suture 360. Likewise, each ofthe cusp legs 358 extends outward and downward from the handle socket352 into proximity with a midpoint of one of the valve cusps 150, and issecured thereto with a lower suture 362. The lower end of each cusp leg358 includes a concavity for mating with the corresponding rod-likestent member 74, as seen in FIG. 26. In this manner, each of the cusps150 and commissures 152 of the valve 40 is securely held in relation tothe others, thus facilitating implantation by the surgeon.

Details of the commissure legs 356 will now being described withreference to FIGS. 23 and 26. Each commissure leg 356 extends outwardfrom the handle socket 352 in a generally rectangular cross-sectioninterrupted by an upwardly-facing inner notch 370 oriented cross-wise tothe leg. And upwardly-facing radial channel 372 having a depth ofapproximately half of each commissure leg 356 extends from about theinner notch 370 to the outermost end of the leg. The inner notch 370 isnot quite as deep as the channel 372, as seen in FIG. 26. The radialchannel 372 divides the upper portion of each commissure leg 356 intotwo walls 374 a, 374 b. An eyehole 376 is formed in one of the walls 374a, and a corresponding outer notch 378 is formed in the other wall 374 baligned with the eyehole. The outer notch 378 is also not quite as deepas the channel 372.

With reference to FIGS. 24 and 26, the upper suture 360 is preferablytied to the eyehole 376 in the first wall 374 a. The suture 360 thenpasses across the channel 372, through the outer notch 378, and ispassed along the inner notch 370, again traversing the channel 372. Thesuture 368 is then passed through a suture-permeable portion of thevalve commissure 152, such as through the connecting band 48. Afterpassing through the commissure 152, the suture 360 is again loopedthrough one or both of the notches 370, 378 and re-tied to the eyehole376. By proper threading of the upper suture 360, each commissure 152can be secured to the commissure leg 356 and easily released byinserting a scalpel blade into the radial channel 372 to sever theportions of the suture therein.

Details of each cusp leg 358 can be seen in FIGS. 23 and 26. A pair oflongitudinal rails 380 a, 380 b are provided on the outer side of eachcusp leg 358. Toward the lower end of the rails 380 a,b, a pair ofaligned eyeholes 382 provide anchoring locations for the lower suture362. A scalpel guide or relief 384 is formed in one of the rails 380 b.As seen in FIG. 24, the lower suture 362 extends downward from theeyeholes 382, passes through a suture-permeable portion of the cusp 150,and is then returned and secured to the eyeholes 382. The relief 384exposes a portion of the lower suture 362 for severing by the surgeonusing a scalpel blade. It will thus be understood that the holder 350can be quickly released from the valve 40 by a series of six scalpelstrokes, with each of the sutures 360, 362 remaining attached to theholder 350 and being withdrawn from the valve 40 as the holder iswithdrawn.

FIGS. 27A and 27B illustrate an alternative holder 390 useful forimplanting the flexible heart valve 40 of the present invention. Theholder 390 is substantially similar to the holder 350 described above,but the ends of each of a plurality of rigid legs for attaching to thevalve cusps are flared, or, more precisely, each lower leg has a widthfrom a hub to a terminal end that is greatest at the terminal end toprovide more surface area to contact the corresponding valve cusp. Thatis, the holder 390 includes a plurality of upper legs 392 having agenerally constant width, and a plurality of lower legs 394 havingflared ends 396, the legs extending from a central hub 398. Again, theupper legs 392 extend radially outward to connect to the valvecommissures 152, and the lower legs 394 angle radially outward anddownward to connect to the valve cusps 150. The flared ends 396 impartgreater stability to the flexible valve 40 during implantation,especially helping to prevent movement of the cusps 150. In addition,the legs 194 remain fairly narrow until the flared ends 396 to maintaingood visibility through the spaces between the plurality of legs. Thatis, for example, the surgeon can continue to view the valve leaflets 42between the legs as a check on valve orientation.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. In particular, though the flexible nature of thepresent heart valve has been described as being particularly suitablefor use in the aortic position, the advantage of flexibility couldequally apply to a valve implanted in other positions, such as themitral position. The scope of the invention is, therefore, indicated bythe appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. A prosthetic heart valve stent, comprising: astent including a plurality of separate stent members adjacentlydisposed around a circle to define a substantially cylindrical volumetherebetween, the stent including a plurality of alternating cusps andcommissures, each stent member including an arcuate cusp region and twoupstanding commissure regions, wherein each pair of commissure regionsof adjacent stent members is juxtaposed to define each stent commissure;and means for pivotally connecting the stein members together at thestern commissures to enable relative movement of adjacent cusps, whereineach stent member is pivotally coupled to move with respect to the otherstent members at the stent commissures.
 2. A prosthetic heart valve,comprising: a flexible, generally cylindrical stent as in claim 1; aplurality of flexible leaflets attached to the stent so as to form aone-way valve within the cylinder; and a flexible band attached alongthe stent and having a free edge extending outward from the stent alongthe alternating cusps and commissures for connecting the heart valve toan anatomical orifice.
 3. A highly flexible heart valve, comprising: astent/leaflet subassembly including a peripheral stent as in claim 1 anda plurality of leaflets disposed therewithin, the stent/leafletsubassembly including alternating cusps and commissures corresponding tothe alternating cusps and commissures of the stent; and a connectingband attached to the stent/leaflet subassembly and following thealternating cusps and commissures, the band having a free edge extendingfrom the stent for connecting the heart valve to an anatomical orifice.4. The heart valve of either of claim 2 or 3, wherein the stent isconfigured to permit the cusps and commissures to move radially in andout.
 5. The heart valve of either of claim 2 or 3, wherein the stentcomprises a cloth-covered rod-like structure.
 6. The heart valve ofclaim 5, wherein the cloth-covering closely surrounds the rod-likestructure and exhibits a flap projecting outward therefrom substantiallythe entire length of the cusps and commissures for connecting to theband and leaflets.
 7. The heart valve of either of claim 2 or 3, whereinthe band comprises a suture-permeable inner member and a cloth outercover, the band exhibiting continuous cusp portions and commissureportions.
 8. The heart valve of claim 7, wherein the suture-permeableinner member comprises a molded silicone structure.
 9. The heart valveof claim 7, wherein the band comprises an outwardly projecting series ofparallel ribs extending continuously along the entire band cusp portionsand commissure portions.
 10. The heart valve of claim 7, wherein thecommissure portions of the band are generally planar and axiallyaligned, and the cusp portions of the band each include an outwardlyangled portion and an inwardly angled ledge.
 11. The heart valve ofclaim 10, wherein the inwardly angled ledge of each cusp portion of theband extends inward a distance sufficient to support the correspondingcusp.
 12. The heart valve of either of claim 2 or 3, wherein the bandincludes arcuate cusp portions generally conforming to the cusps, andthe band includes commissure portions therebetween each having aninverted U-shape to define a downwardly opening gap that enhancesflexibility of the valve by permitting relative cusp movement.
 13. Aprosthetic heart valve, comprising: a plurality of flexible leafletseach having an arcuate cusp edge and a coapting edge; and a stent as inclaim 1, the leaflets being attached to the stent within the volume andthe cusps being free to move with respect to one another about thecommissures.
 14. The heart valve of claim 13, wherein the cusps of thevalve are hingedly connected to each other.
 15. The heart valve of claim14, wherein each pair of commissure regions is connected with sutures toenable relative movement of adjacent cusp regions.
 16. The heart valveof claim 14, wherein each commissure region is connected to pivot abouta first axis which is fixed with respect to a second axis about whichthe adjacent commissure region pivots, both the first and second axesbeing generally radially oriented with respect to a central axis of thecylindrical volume.
 17. The heart valve of claim 16, wherein the firstand second axes are coincident.
 18. The heart valve of claim 17, whereineach commissure region terminates at an arcuate tip, the valve furtherincluding coupling members having an arcuate channel therein, thecoupling members receiving the arcuate tips of the commissure regionsand permitting relative sliding movement about a pivot axis defined bythe arcuate channel.
 19. The heart valve of claim 16, wherein eachcommissure region terminates at a generally circular tip, the valvefurther including coupling members having a pair of spaced pins providedthereon that defined the first and second axes and about which thecircular tips of each commissure region pivot.
 20. The heart valve ofclaim 14, wherein the valve includes a plurality of pliable couplingmembers each of which couples to a pair of adjacent commissure regionsto permit relative movement therebetween.
 21. The heart valve of claim20; wherein each commissure region terminates at a generally linear tip,the pliable coupling members comprising pliable tubular sleeves closelyfitting over the linear tips.
 22. The heart valve of claim 13, whereinthe means for connecting the stent cusps together comprises sutures. 23.The heart valve of claim 13, wherein the means for connecting the stentcusps together comprises a flexible material interface.
 24. The heartvalve of claim 13, where the means for connecting the stent cuspstogether comprises a bioresorbable Structure.
 25. The heart valve ofclaim 13, wherein the stent comprises a cloth-covered rod-likestructure.
 26. The heart valve of claim 25, wherein the cloth-coveringclosely surrounds the rod-like structure and exhibits a flap projectingoutward therefrom substantially the entire length of the cusps andcommissures.
 27. The heart valve of claim 26, wherein the flap has awidth that varies along the cusps and commissures of the stent, the flapbeing narrower in the cusps.
 28. The heart valve of claim 26, furtherincluding a flexible band attached along the stent flap and having afree edge extending outward from the stent along the alternating cuspsand commissures for connecting the heart valve to an anatomical orifice.29. The heart valve of claim 28, wherein the cusp edges of the leafletsare attached between the band and the stent flap.
 30. The heart valve ofclaim 28, wherein the band exhibits continuous cusps and commissures,the cusps of the band each including an outwardly angled portion and aninwardly angled ledge extending inward a distance sufficient to supportthe corresponding cusp of the stent.
 31. The heart valve of claim 25,wherein the rod-like structure is made of a polymer.
 32. The heart valveof claim 13, wherein each separate stent member is separatelycloth-covered.
 33. The heart valve of claim 32, wherein each upstandingcommissure region terminates in a substantially circular bent tip,adjacent bent tips of each separate member being juxtaposed and suturedtogether through the respective cloth coverings.
 34. The heart valve ofclaim 13, wherein each leaflet includes an arcuate cusp edge terminatingat outer tips joined to the stent commissures, and a coapting edge thatis defined by two relatively angled lines joined at an apex midwaybetween the two tips.
 35. The heart valve of claim 34, wherein eachleaflet is made of pericardial tissue.
 36. The heart valve of claim 34,wherein the arcuate cusp edges gradually become asymptotic at the tips.37. The heart valve of claim 34, further including an outwardly angledtransition edge from the arcuate cusp edges to the tips.
 38. The heartvalve of claim 37, wherein a generally linear edge is defined betweeneach outwardly angled transition edge and the corresponding tip defininga generally trapezoidal tab adjacent the tips.
 39. The heart valve ofclaim 2 or 3 wherein each leaflet includes an arcuate cusp edgeterminating at outer tips joined to the stent commissures, whereinadjacent tips are joined not to each other but to portions of the stentthat are permitted to move with respect to one another.
 40. The heartvalve of claim 39, further including a flexible band attached along thestent and having a free edge extending outward from the stent along thealternating cusps and commissures for connecting the heart valve to ananatomical orifice, the band defining an inverted U-shape at the stentcommissures with a gap formed between portions of the stent that arepermitted to move with respect to one another.
 41. The heart valve stentof claim 1, wherein the means for connecting the stent members togethercomprises sutures.
 42. The heart valve stent of claim 1, wherein themeans for connecting the stent members together comprises a flexiblematerial interface.
 43. The heart valve stent of claim 1, where themeans for connecting the stent members together comprises abioresorbable structure.
 44. The heart valve stein of claim 1, whereineach commissure region is connected to pivot about a first axis which isfixed with respect to a second axis about which the adjacent commissureregion pivots, both the first arid second axes being generally radiallyoriented with respect to a central axis of the cylindrical volume. 45.The heart valve stent of claim 1, wherein each commissure region isconnected to pivot about a first axis which is fixed with respect to asecond axis about which the adjacent commissure region pivots, both thefirst and second axes being generally radially oriented with respect toa central axis of the cylindrical volume; wherein each commissure regionterminates at a generally circular tip, the stern further includingcoupling members having a pair of spaced pins provided thereon thatdefine the first and second axes and about which the circular tips ofeach commissure region pivot.
 46. The heart valve stent of claim 44,wherein the first and second axes are coincident.
 47. The heart valvestent of claim 1, wherein each commissure region terminates at anarcuate tip, the stent further including coupling members having anarcuate channel therein, the couping members receiving the arcuate tipsof the commissure regions and permitting relative sliding movement abouta pivot axis defined by the arcuate channel.
 48. The heart valve stentof claim 1, wherein the valve includes a plurality of pliable couplingmembers each of which couples to a pair of adjacent commissure regionsto permit relative movement therebetween.
 49. The heart valve stent ofclaim 48, wherein each commissure region terminates at a generallylinear tip, the pliable coupling members comprising pliable tubularsleeves closely fitting over the linear tips.
 50. The heart valve stentof claim 1, wherein each stein member is flexibly coupled with respectto the other stent members at the stent commissures.
 51. The heart valvestent of claim 50, wherein each stent member is elastically coupled withrespect to the other stent members at the stent commissures.